How do you define "sees the win"???D Sceviour wrote:If null move search is turned off, my program finds the win in a depth of 25.Joost Buijs wrote:Every good chess player sees immediately that Black is dead lost, many engines just don't find it because there is zugzwang (null-move).
There have been previous comments about identifying more zugzwang positions for null move search, especially for minor piece endgames. Currently, null move search is typically rejected for pawn endgames only. Rejecting a null move search for minor piece endgames can add other problems related to lack of depth. Is there any research going on in the area of formulating further null move search zugzwang conditions?
One idea I have experimented with is examining the absence of free pawns in a position. (A free pawn is a pawn that can advance safely). However, the positions are still too complex to combine with minor piece endgames.
I let Crafty search, at 100M nodes per second, for over an hour. It starts at +2 quickly, then at depth 44 the score starts to climb (about 30 seconds). And by the time it gets to depth 50, the score is +4 (best move has been a5 all along). But at depth 51 there is a big fail high and the score drops back to the original +1.75 and sticks there through depth 53 where I stopped it. That's certainly good for white, but not a clear and convincing win. Here is the last output I saved:
Code: Select all
52 30:05 1.75 1. ... a5 2. Kd3 Kh5 3. Ke2 Kg6 4. Ne3 Kh5
5. Kd1 Bb2 6. Ng2 Kg4 7. Kxd2 Be5 8. Kd3
Kh5 9. Kc4 Bc7 10. Kb5 Kg6 11. Ne1 Bg3
12. Nf3 Bc7 13. Kc4 Bf4 14. Ne1 Be5
15. Ng2 Bc7 16. Kd3 Kh5 17. Kd2 Be5
18. Ke3 Bc7 19. Kd4 Kg6 20. Ne1 Bf4
21. Nf3 Bg3 22. Ke3 Bd6 23. Kd4 Bg3
24. Ke3 Bd6 25. Ke4 Bg3 26. Kd4 Bd6
27. Kd3 Bg3 28. Ke2 Bf4 29. Kd1 Kh5
30. Ke2 Bc7 31. Kd3 Kg6 32. Kd4 Bd6
33. Ne1 Bg3 34. Ng2 Bc7 35. Ne1 Bf4
36. Ng2 Bg3 37. Kd3 Bd6 38. Ne1 Bg3
39. Nf3 Kh5 40. Kc4 Bb8 41. Nd4 Be5
42. Nf5 Kg6 43. Ne7+ Kh5 44. Kd5 Bc3
45. Kd6 Kxh4 46. g6
